Method of making a flexible closure incorporating an alarm system

ABSTRACT

A flexible closure, for use in an alarm system is provided in which a conductive sensing element is interlaced with fiber matrix material to provide a network over at least part of the closure. The interlacing is preferably by means of knitting a conductive wire together with a yarn which forms the matrix of the closure. The closure may further include a protective outer layer on one or both faces of the closure.

The invention relates to a method of making a flexible closure and to aflexible closure for incorporation in an alarm system.

In my earlier publication, WO 87/06749, I have disclosed an alarm systemfor flexible closures consisting of a network of conductive sensingelements which are attached to or incorporated into the closure. If theclosure is cut to any significant extent, the elements will be disturbedor broken causing a change in the current flowing therein or a change inthe resistance. This exchange is used to trigger an alarm, alerting theowner to any attempted unauthorized access to the area enclosed by theflexible closure.

In that prior arrangement, the network of conductive sensing elements isstitched, bonded or webbed to a layer of material which forms theflexible closure. It is necessary to use such a layer on which to laydown the network. In an attempt to make it more difficult to detect oneof the elements of the network and subsequently attempt to by-pass thealarm system, I disclosed in my European Publication No. 0359762 analarm system in which the conductive sensing elements compriseconductors in a common outer sheath together with at least one otherdummy conductor.

Other prior arrangements for deterring unauthorized access include U.S.Pat. Nos. 3,051,935 and 4,293,778. U.S. Pat. No. 3,051,935 discloses ascreen structure comprising a sheet of non-conductive screen materialsecured in a frame with strands of conductive wire then being woventhrough the screen material. The wire and the screen material arepreferably coated with a vinyl material so as to be visiblyindistinguishable. U.S. Pat. No. 4,293,778 discloses an anti-theftscreen construction in which lengths of conductive wire are laid on amesh screen and then mechanical bonded to the screen at the points ofintersection. However, these prior arrangements suffer from thedisadvantage that the screens are rigid, moreover all the priorarrangements suffer from the disadvantage that the conductive elementsare applied to a preformed substrate.

It is an object of the present invention to provide an improved methodof making a flexible closure incorporating a conductive sensing elementfor an alarm system and to a flexible closure incorporating a conductivesensing element.

According to the invention, there is provided a method of making aflexible closure for incorporation in an alarm system the methodcomprising interlacing a conductive sensing element with fibre materialforming the matrix of the closure so that the interlaced conductivesensing element provides a network over at least part of the closure.Preferably the network is formed integrally with the formation of thematrix of the closure thereby simplifying its manufacture. Theinterlacing may be by means of knitting, weaving, crocheting or otherentwining of materials or non-woven matrix material may be stitchedthrough the matrix.

In a preferred embodiment, the closure is knitted. The closure may beknitted from a mixture of the conductive sensing element or elements andother material forming the matrix of the closure such as cotton, nylon,polyester, wool, fibres, etc. The interlacing of the conducting sensingelements renders the conductive sensing elements more difficult todetect. The term `fibre` includes any elongate strand, filament, yarn orthe like.

The conductive sensing elements may be of any type of conductive fibreor filament, e.g. carbon fibre, glass fibre. Preferably, the conductivesensing elements are of copper tinsel. The copper core may be sheathedin conventional PVC material or in ELVALOY resin material or any othersuitable insulating material.

The closure may be interlaced into any shape and may include open areasor holes. The method also may include applying one or more protectivelayers to the or each face of the closure.

The invention also includes a flexible closure, for use in an alarmsystem, comprising a conductive sensing element interlaced with fibrematrix material providing a network over at least part of the closurefor connection in an alarm circuit for sensing disturbance of theclosure. If desired, the closure may further include a protective outerlayer of plastics or any other material on one or both faces of theclosure.

According to another aspect of the invention there is provided an alarmsystem for deterring unauthorized access to an area protected by aflexible closure comprising a conductive circuit including a conductivesensing element interlaced with fibre material forming the matrix of theclosure, the alarm system, in use, being operable in response todisturbance of the flexible closure by disturbance of the conductivesensing element in the circuit.

If desired, the conductive sensing element may be enclosed with a secondconductive sensing element in a common outer sheath, possible togetherwith at least one other dummy `conductor` of substantially identicalappearance. Equally there could be dummy elements and conductiveelements. The conductive sensing element suitably has substantiallysimilar appearance to the matrix material to minimize the possibility ofeasy detection.

Flexible closures made in accordance with the invention will now bedescribed by way of example with reference to the accompanying drawingswherein:

FIG. 1 is a schematic view of part of a woven flexible closure inaccordance with the invention;

FIG. 2 is a perspective view of part of the flexible closure of FIG. 1;

FIG. 3 is an elevation of the flexible closure of FIG. 1 shown, in use,on a curtain-sided goods vehicle;

FIG. 4 is a schematic view of part of another knitted flexible closuremade in accordance with the invention; and,

FIG. 5 is a schematic view of one method of manufacture of a flexibleclosure by knitting.

The flexible closure (10) in FIGS. 1 to 3 comprises a woven matrix orbase material (12) having a network of conductive sensing elements (14)interwoven therewith. The woven material (12) comprises a network ofwoven strands (16) of a given material, such as polyester.

In FIG. 3 the flexible closure (10) is shown in use on a curtain-sidedgoods vehicle (18). The closure (10) is covered by a front sheet (20)(shown partially cutaway). If desired, the flexible closure may providethe curtain itself. The flexible closure is also applicable to theprotection of other areas and items, for example, it may be used toenclose military equipment during storage or may form a boat cover orvehicle soft roof or be formed into a portable container for carryingvaluable materials.

The flexible closure in FIG. 4 is an alternative arrangement inaccordance with the invention. In that Figure, the closure (10)comprises strands of a material (15), such as polyester, knittedtogether with conductive sensing elements (14) in a rib-typeconfiguration or other knitted structure. As illustrated in FIG. 4, theknitted sensing element 14 follows a sinuous path with horizontal andvertical components. The closure could be knitted in any otherconfiguration of weft or warp knitting.

The conductive sensing elements (14) may comprise any suitableconductive material such as carbon fibre or glass fibre. The sensingelement (14) can be electrically conductive or optically conductive andthey could be one or more strands, one or more sheathed cores.

In use, one or more sheathed cores of copper tinsel are knitted togetherwith polyester base material. Once knitted, the wired and polyesterclosure is covered with a PVC material (or other material) cover overthe top. If desired, a cover may also be fitted underneath to form alamination or sandwich-type layer in which the wired closure isencapsulated between PVC layers. The closure is then provided with aseries of holes around the perimeter of the knitting and the or eachcover which are fitted with eyelets or alternative means of closure withor without holes.

In order to facilitate connection of the or each cover sheet theflexible closure may have a border for ease of fixture of the or eachprotective cover to the knitted closure. The covers can be fitted eitherby sewing together or by sewing a strip of material, eg. PVC, to theknitted closure and then welding the strip to the top and/or bottomcover. Alternatively, the flexible closure can be fixed to the or eachcover by lamination, by heat or by adhesive, or by rivet or other formof fixture.

Once the flexible closure has been completely formed, with or withoutprotective cover layers, the conductive sensing elements (14) areconnected together at their ends so as to form an electrical circuitacross the closure (10) for use in triggering an alarm in case ofunauthorized tampering. The circuit can be connected directly into aknown alarm circuit or could be connected to a transmitter operable totransmit an alarm signal in the case of disturbance.

In the preferred arrangement one or more insulated conductive wires isknitted with polyester. However, knitting involves intermittent feedingof material as the slide moves to and fro across the needle bed of theknitting machine with the material accelerating from still to maximum ina very short time. With knitting yarns this is not really a problembecause the yarn is able to stretch which absorbs the shocks ofacceleration. However, conductive wire is effectively non-stretchableand use in a conventional manner on a knitting machine can lead to thewire breaking.

In FIG. 5 there is shown a schematic apparatus for feeding conductivewire to a conventional flat bed knitting machine (not shown) which isdesigned to absorb acceleration shocks and prevent wire breakage. Inpractice, the feed apparatus (30) shown in FIG. 5 is mounted on asuitable framework but, for schematic purposes and for clarity, thisframework has been omitted since it forms no part of the invention.

In FIG. 5 a source of conductive wire (32) is provided on a drum (34).Located above the drum (34) is a flyer (35) mounted to the framework bysuitable screws of bolts (not shown). The flyer (35) is for unwindingthe conductive wire (32) from the drum (34) as required and comprises aflyer arm (38) with ceramic guides (40). The flyer arm (38) is rotatableby means of the unwinding process of the wire from the drum (34) and themomentum of the flyer arm (38) may be automatically varied by a magneticbrake (44), according to the speed at which the conductive wire (32) isbeing unwound.

From the flyer (36) the conductive wire (32) is passed over a series ofpulleys (45,46,48,50) to a yarn storage tambour (52) of known design.The tambour (52) is a retractable drum and stores conductive wire (32according to the length of stroke of the slide of the knitting machineand includes a plurality of movable fingers (54) to ease release of thenon-stretch wire (32). Pulleys (45,48,50) are fixed and serve as guidesbut pulley (46) is movable as indicated by arrow (56).

The movable pulley (46) has an axle (58) which is received in sidechannels (60) of a framework (52) (only the far side channel (60) beingshown). The pulley (46) is free to float in the channels (60) in thedirection of arrow (56) within limits determined by top and bottom stops(64,55). In use, the movement stroke of the floating pulley (45) takesup any slack and serves as a `reservoir` for the tambour (52) during theintermittent feed requirement of the knitting machine.

The feed apparatus (30) also includes, adjacent the knitting machine, aguiding eye (68) and a conventional knitting tensioning spring (70).

In use, conductive wire (32) is unwound from the drum (34) by means ofthe flyer (36). The wire (32) is drawn over pulleys (44,46,48,50) to thetambour (52) on which a length of wire is stored. The wire then passesto a guiding eye (68) where it is united with a polyester yarn (72). Theyarn (72) and wire (32) then pass through the eye of tensioning spring(70) to the slide of the knitting machine to be knit in known manner. Aswire (32) is drawn by the knitting machine, the wire (32) is eased fromthe tambour (52) by the movable fingers (54) and the pulley (45) floatsup and down according to the acceleration of the knitting machine andproviding a `reservoir` for the tambour (52) absorbing shock andpreventing wire breakage.

Although only one conductive element is shown being supplied to theknitting machine, any number may be knit into a polyester fabric matrix,preferably four.

I claim:
 1. An alarm system for deterring unauthorized access to anarea, comprising:a matrix of fibre material interlaced with a conductivesensing element forming a closure for said area, the conductive sensingelement being knitted or crocheted integrally with the fibre material ofthe matrix; the interlaced conductive sensing element providing anetwork over at least part of the closure; and alarm means connected ina circuit with said sensing element for providing an alarm in responseto disturbance of the closure by disturbance of the conductive sensingelement in the circuit.
 2. A closure, for use in an alarm systemcomprising:a flexible cover member for at least partially enclosing anarea to be protected; the cover member comprising a matrix of fibrematerial interlaced with a conductive sensing element; the conductivesensing element being knitted or crocheted integrally with the fibrematerial of the matrix and comprising means for providing a network overat least part of the closure for connection in an alarm circuit forsensing disturbance of the closure.
 3. A closure according to claim 2,including a protective outer cover sheet covering at least one face ofthe closure.
 4. A closure according to claim 2, wherein the conductivesensing element is knitted together with a yarn to form a flexible covermember of knitted configuration.
 5. The closure as claimed in claim 2,wherein the conductive sensing element is insulated.
 6. The closure asclaimed in claim 2, wherein the conductive sensing element follows asinuous path through the matrix, the path having horizontal and verticalcomponents.
 7. A method of making a closure for incorporation in analarm system the method comprising interlacing a conductive sensingelement with material forming the matrix of the closure so that theinterlaced conductive sensing element provides a network over at leastpart of the closure characterised in that the conductive sensing elementis knitted or crocheted integrally with fibre material of the matrixduring formation of the matrix of the closure.
 8. A method of making aflexible closure according to claim 7, comprising providing a source ofat least one insulated conductive sensing element, providing a source ofa yarn for forming a matrix of the closure, feeding the conductivesensing element and yarn to a knitting machine and knitting theconductive sensing element with the yarn to form the flexible closure.9. A method according to claim 8, wherein the step of feeding theconductive sensing element comprises passing the conductive sensingelement from the source to an intermediate storage device and shockabsorbing means for accommodating irregularities in demand due toacceleration/deceleration of the knitting machine.
 10. A methodaccording to claim 9, comprising providing a floating pulley between thesource and the intermediate storage device for forming said shockabsorbing means.
 11. A method according to any one of claims 8 to 10,wherein the source of insulated conductive sensing element comprises adrum and the sensing element is unwound from the drum by means of aflyer.